High frequency excitation



March 28, 1944.

A. H. TOEPFER HIGH FREQUENCY EXCITATION Filed June 23, 1939 Load - WITNESSES:

Patented Mar. 28, 1944 2,345,162 HIGH FREQUENCY EXCITATION Adolph H. Toepfer,

Wilkinsburg, Pa.,

assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh,

Pennsylvania Application June 23, 1939', Serial N0.

3 Claims.

My invention relates to electric discharge apparatus and has particular relation to electric discharge devices of the insulated-ignition-electrode type.

In discharge devices constructed in accordance with the teachings of the prior art, the ignition electrode is a conductor sealed in a glass jacket. The electrode is in contact with the pool which forms the cathode of the device, the glass serving as insulation between the conductor and the pool. A discharge is ignited by impressing an alternating potential between the conductor and the pool. Discharge devices of the insulated-ignitionelectrode type are designed to carry substantial current and develop substantial In using the prior art devices it has been cause of the excessive temperatures to which the ignition electrode is subjected, the insulation develops fissures when the apparatus operates for only a short time. The cathode and the ignition conductor are then interconnected and the useful life of the device is terminated. The use of mercury in a quartz tube for ignition purposes has been suggested. However, this arrangement has proved unsatisfactory because the mercury becomes turbulent when in operation, and the properties of the electrode are irregular.

It is accordingly an object of my invention to provide an ignition electrode capable of withstanding the heat developed during operation for a discharge device of the insulated-ignition-electrode type.

According to my invention, the ignition electrode consists of a solid conductor such as a steel wire, a grap 'te rod or a dried and fired carbon mass enclosed in an insulating jacket of quartz. I have found, by carrying out a series of experiments, that the quartz withstands the heat developed in the discharge device and does not crack even if discharge current flows continuously for many hours. A less propitious arrangement which may be used in accordance with my invention when the loading of the discharge valve is intermittent is an insulating jacket of glass, reinforced by imbedding silicon carbide crystals.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawing in which,

Pa., a corporation of Figure l is a diagrammatic view showing a circuit utilizing a discharge device embodying my invention;

Figs. 2 and 3 are diagrammatic views showing a modified igniter in accordance with my invention.

In the system shown in Figure 1, load 3 of any general type is supplied from a source 5 of alternating current, which may be of the usual commercial, cycle, type, through an electric discharge device 'I. The device 1 comprises a pair of hollow, coaxial metallic cylinders 9 and H joined at the ends. During operation, a cooling fluid is conducted through the space between the cylinders 9 and H and prevents the structure from becoming over-heated. The inner cylinder 9 is preferably composed of stainless steel and near its upper end, by welding or otherwise in such manner joint is vacuum tight. A flange l5 composed of a cobalt-nickel-iron alloy, known in the art as Kovar alloy, is secured to the inner surface of the ring l3. A glass ring I1 is sealed to the alloy flange 13 and a cobalt-nickel-iron alloy cap [9 is sealed to the glass. Through the cap IS a metallic bar 2| is sealed, and the bar carries at its lower end, a block Z3 of conductive material such as carbon or a metal which serves as the anode for a discharge device.

Near the lower end of the internal cylinder 9, a metallic disc 25 is sealed. The disc is provided with an opening 21 and a cobalt-nickel-iron alloy eyelet 29. Through the opening 21, a metal tube 3| is sealed and a glass sleeve 33 is sealed through the eyelet 29. A conducting lead 35 of the ironnickel-cobalt alloy is sealed through the sleeve 33 and a wire 31 of steel or other conducting material is welded to the rod. The wire 31 is bent over to form a hook-like structure and at its free end a quartz jacket 41 is fastened. The quartz should have a thickness no greater than A mercury pool '13 is disposed on the disc 25 and serves as cathode for the discharge device. The quartz jacket ii on the wire 31 dips into the mercury pool 13 in such manner that the tip of the wire extends below the surface of the mercury. The metal tube 3! is used for exhausting the space between the inner cylinder 9, the disc 25, and the ring l3 and also for properly adjusting the height of the mercury 43.

Because the quartz jacket 4| is thin the temperature gradient developed in the quartz when an arc is fired between the pool 43 and the anode 23 is small. Therefore, no thermal stresses and resultant fissures develop in the Jacket. I have found that if the jacket thickness is substantially mch, substantial stresses are dewire 31.

In lieu of a wire a graphite rod or a mass 44 of dried and fired. carbon may be disposed in the jacket 4| as shown in Fig. 2.

While the quartz jacket is used in the preferred carbide crystals embedded therein as shown in silicon-carbide jacket has substantial strength and is not ruptured by the stresses developed during operation.

45, the secondary 47 of which is connected be tween the conductor and the cathode. The primary #9 of the transformer is connecte with a capacitor across the fixed and movable terminals 53' and 55, respectively, of a spark gap. The terminals 53 and 55 are successively work 63 results in the flow of a high frequency network. Theimpulse is impressed between the ignition conductor 31 and the cathode 43 through the transformer 45.

The discharge the first high frequency impulse is impressed, or several impulses may be plied to the solenoid 51 order of ampere.

has a peak value of the When the discharge is inibe. re by the claims.

stricted except insofar as' is necessitated prior art and by the spirit of the appended I claim as my invention: 1. An electric discharge device comprising a cathode of the pool type and an ignition electrode consisting of a conductor enclosed in an insulating coating of quartz at most, :32" in thickness in engagement with said cathode.

2. An electric discharge device comprising a insulating coating of quartz at most, 3% in thickness in engagement with said cathode. 

